1. Field
The presently disclosed subject matter relates to reliable semiconductor light source apparatuses, and more particularly to reliable reflective typed semiconductor light source apparatuses having a phosphor plate and two reflector layers, which can prevent a degradation of optical characteristics caused by heats generated from the phosphor pale and a first reflector layer and can efficiently radiate the heats using a second reflector layer and the like, and which can also emit various color lights having a large amount of light intensity including a substantially white color tone in order to be able to be used for general lighting, a stage light, a street light, a projector, etc.
2. Description of the Related Art
A range of application for semiconductor light source apparatuses, which may emit various color lights by combining a wavelength-converting material such as a phosphor layer with a semiconductor light-emitting device such as an LED, have expanded to various fields such as vehicle lamps, general lighting, street lighting, etc. because brightness of the semiconductor light source apparatuses have improved. As a method for such the semiconductor light source apparatuses, a transmission type, which emits a mixture light having a color tone from a light-emitting surface of the phosphor layer by entering an exciting light into the phosphor layer from an incident surface located opposite the light-emitting surface, is well known.
As another method, a reflective type, which emits a mixture light having a color tone from a light-emitting surface of a phosphor plate including a reflector surface by entering an exciting light into the phosphor plate from an incident surface located on the same reflector surface and by reflecting the mixture light with the reflector surface, is well known. The reflective type may emit the mixture light having a high light-intensity mainly by using the mixture light reflected from the reflector surface, and therefore has been expected to expand in application.
FIG. 11 is a schematic structural view showing a first conventional semiconductor light source apparatus of the reflective type disclosed in Patent document No. 1 (Japanese Patent Application Laid Open JP2012-64484), and a conventional light source apparatus similar to the first conventional semiconductor light source apparatus is also disclosed Patent document No. 2 (U.S. Pat. No. 8,556,437). The patent documents No. 1 and No. 2 are disclosed by a same inventor, and are owned by Applicant of this disclosed subject matter.
The first conventional semiconductor light source apparatus includes: a reflector 84; a phosphor ceramic 83 arranged on the reflector 84 via a transparent adhesive material 85; a semiconductor light-emitting device 81 having an optical axis 82 located adjacent the phosphor ceramic 83, the optical axis 82 intersecting with the phosphor ceramic 83; a mixture light 86 having a color tone emitted from a light-emitting surface of the phosphor ceramic 83 by entering an exciting light emitted from the semiconductor light-emitting device 81 into the phosphor ceramic 83 and by reflecting the mixture light using at least one of the reflector 84, the transparent adhesive material 85 and the phosphor ceramic 83; and an optical lens 87 located in a direction of the light-emitting surface of the phosphor ceramic 83, and projecting a prescribed light distribution pattern using the mixture light 86.
In the first conventional semiconductor light source apparatus 80, a heat generated from the phosphor ceramic 83 by the excited light emitted from the semiconductor light-emitting device 81 may mainly radiate from the reflector 84, which is made from a metallic plate, and therefore may not degrade the phosphor ceramic 83. However, because the heat generated from the phosphor ceramic 83 may degrade the transparent adhesive material 85, an adhesive intensity between the phosphor ceramic 83 and the reflector 84 may degrade and a reflectivity of the reflector 84 may decrease. Hence, the heat generated from the phosphor ceramic 83 may cause optical characteristics of the semiconductor light source apparatus 80 to gradually deteriorate.
A second conventional semiconductor light source apparatus, in which each of marks 85 and 84 shown in FIG. 11 is respectively replaced with a reflector layer that is directly formed underneath the phosphor plate (83) and a heat sink made from a metallic material such as aluminum and the like, is disclosed in Patent document No. 3 (Japanese Patent Application Laid Open JP2013-130605). The second conventional light source apparatus does not include the transparent adhesive material 85 shown in FIG. 11, and therefore may prevent the above-described degradation of the optical characteristics thereof, which is caused by the transparent adhesive material.
However, although a reflection ratio of the reflector layer such as silver (Ag) and the like may be approximately 90 percentages or more, light absorbed into the reflector layer without a reflection may vary a heat. For example, when the excited light having a density of 30 W/mm2 enters into the reflector layer with a reflection ratio of 97 percentages, the light of 3 percentages absorbed into the reflector layer may vary a heat having a heating density of 0.9 W/mm2.
In addition, when the excited light entering into the phosphor plate is wavelength-converted by a phosphor contained in the phosphor plate, the phosphor plate may develop a heat. The phosphor plate may generally include a transparent resin such as a silicone resin and the like to contain the phosphor therein, and a part of the transparent resin having a relatively low thermal conductivity may contact with the reflector layer. Accordingly, the above-described heats generated from the phosphor plate and absorbed into the reflector layer may degrade the transparent resin, and therefore may cause a degradation of optical characteristics of the second conventional semiconductor light source apparatus in common with the first conventional semiconductor light source apparatus.
The above-referenced Patent Documents are listed below and are hereby incorporated with their English abstracts in their entireties.
1. Patent document No. 1: Japanese Patent Application Laid Open JP2012-64484
2. Patent document No. 2: U.S. Pat. No. 8,556,437
3. Patent document No. 3: Japanese Patent Application Laid Open JP2013-130605
The disclosed subject matter has been devised to consider the above and other problems, characteristics and features. Thus, an embodiment of the disclosed subject matter can include semiconductor light source apparatuses, which can emit various color lights having high brightness and can efficiently radiate a heat, even when a high power semiconductor light source is used under a large current as a light source. In this case, an excited light emitted from a high power semiconductor light source can be efficiently wavelength-converted by a phosphor plate without a reduction of light intensity, because the phosphor plate is substantially located on a first reflector layer and does not include a substantially resin component.
In addition, a second reflector layer located under the first reflector layer can be constructed as a radiating layer to further improve a radiating efficiency and permanence of the phosphor plate even when the high power semiconductor light source is used under a large current. Thus, the semiconductor light source apparatuses can also emit the various color lights having high brightness from a light-emitting surface of the phosphor plate, and therefore can be employed for various lighting units such as general lighting, a stage light, a street light, a projector, etc.